I wonder if grocery stores experience net gains, net losses, or neither from snowstorms.  The rush on grocery stores before the storm is well-accepted; I think it is overstated.  But, as in this weekend, normal Saturday shoppers might shift to Friday, making Friday busier than ever.  Proverbially staples like bread, milk, and eggs are wiped out; but barring power outages all that food is still OK, only now at customers’ homes, so demand is less for a few days.  I bet the effect on stores is a slight negative; they lose some sales from cleaned out counters before the storm, but do not quite recover post-storm.